1. Technical Field
This invention relates generally to knee braces, and more particularly to knee braces worn externally about a knee joint for supporting and manipulating the knee joint.
2. Related Art
As is known, and shown in FIGS. 1 and 2, a knee joint 10 is the largest joint in the body and has a unique anatomy due to its unusual movement. Though it may appear to the casual observer as a simple joint, in actuality, it is extremely complex. The complexity results from the fact that the knee joint 10 has femoral condyles 12 that rotate downward and slightly medial with each flexion of a lower leg portion, then rotate slightly backward and upward with the extension of a lower leg portion 14 relative to an upper leg portion 15. Accordingly, the rotation of the knee joint results in a three-dimensional movement, rather than a two-dimensional movement seen in more simple joints, such as an elbow, for example.
The knee joint 10 is made up of three bones which interact with one another to provide the three dimensional movement of the joint. One of the bones is the largest bone in the body, the femur 16, which supports the upper leg portion 15 and is commonly referred to as the thighbone. Two others are the tibia 18, which is commonly referred to as the shinbone, and the patella 20, which is commonly referred to as the kneecap. In addition to the femur 16, the and tibia 18 has ends referred to as condyles, each of which are bifurcated into lateral and medial condyles 22. The femoral condyles 12 and the tibial condyles 22 are separated from direct frictional engagement with one another by separate layers of cartilage, commonly referred to as the lateral and medial meniscus 24, 25. Each meniscus 24, 25 is generally C-shaped, and fits into the joint between the femoral condyles 12 and the tibial condyles 22 to facilitate rotating and sliding movement therebetween. To further facilitate proper movement and reduce friction within the knee joint 10, a synovium tissue, which produces synovial fluid, lubricates the joint. Of course, the knee joint 10 includes many tendons and ligaments to produce the movement of the knee, and to stabilize its alignment, some of which are discussed hereafter.
The femoral condyles 12 are generally quite rounded and are bifurcated to form an inverted V-shape groove 26 traversing anterior and posterior sides of the knee. The respective tibial condyles 22 are generally somewhat less rounded, and produce what is commonly referred to as the tibial plateau. The tibial plateau also has a small V-shaped groove 28 traversing the anterior and posterior sides of the knee in generally mirrored relation to the groove 26 in the femur 16. The middle portion of the tibial plateau has a slight up cropping on which anterior (ACL) and posterior (PCL) cruciate ligaments attach. The cruciate ligaments stabilize the knee front to back.
The medial meniscus 25 (on the inside portion of the knee) and the lateral meniscus 24 (on the outside portion of the knee) are in the shape of cartilage rings which circumvent the edges of the tibial condyles 22 to create a cushion for the tibial plateau. The rings define generally convex receptacles for receipt of the rounded femoral condyles 12 throughout their range of motion. Preferably, the femoral condyles 12 are maintained in a generally snug fit within the receptacles to prevent slop or wobbling of the femoral condyles 12 relative to the tibial receptacles. Accordingly, in a properly functioning knee joint, the femur 16 articulates relative to the tibia 18 in a smooth and stable motion.
The patella 20 functions to tension the knee joint 10 throughout its range of motion, as well as to protect the joint from impact forces. The patella 20 is maintained in position to follow a slight deviation medially and laterally while remaining within in the V-shaped grooves 26, 28 between the femoral and tibial condyles 12, 22. Proper alignment of the patella 20 during articulation of the knee joint 10 prevents damage to the tibial condyles 22 and the separate meniscus 24, 25 as it tracks across them. The patella 20 also tracks with a slight rotation in its upward and downward movements. The patella 20 fits into the inverted V-shaped groove 26 of the femur 16 and tracks over the smaller frontal V-shaped groove 28 of the tibia 18 (FIG. 5). The shape of the patella 20 is roughly that of an inverted pear, which is rounded and smooth on an outer surface 29, and providing a generally V-shaped projection 30 on an underside to define laterally spaced, generally concave portions 32 which track over the femoral condyles 12. The precise shape of the patella 20 and the underside projection 30 and curvatures 32 varies from person to person. In some people, the projection 30 is generally pronounced and in others it is more subtle. It is believed that people having a more pronounced and sharp projection 30 on the underside of the patella 20 encounter more problems with tracking of the patella 20 during articulation of the knee joint 10.
The knee joint 10 is designed to withstand generally large forces vertically, typically up to 400 pounds or more, however, it is not designed to withstand significant side forces, whether originating laterally or medially. With normal usage, the knee joint 10 will generally last a lifetime, yet one-quarter million Americans require knee replacement surgery every year. Accordingly, something out of the ordinary generally must happen to the knee joint 10 for it to require medical attention, such as surgical repair or replacement.
Unfortunately, the high degree of mobility of the knee joint 10 means it is more susceptible to being shifted off its midline plane 34 either laterally or more commonly, medially. This condition is commonly known as patello-femoral syndrome (FIGS. 3, 4 and 6). Once the knee joint 10 is shifted off the mid-plane 34, an individual's body weight, in addition to increased vertical compression loads generated in use, generates a side or shear load due to the misalignment. The shear load results in laterally opposite loads that are not desirable for normal operation of the knee joint 10. This new, skewed force vector will continue to create additional shear forces throughout the knee joint 10 with each and every flexion, thus, further skewing the shear force vector angle from its normal vertical direction. Eventually, the shear forces cause accelerated wear to the aforementioned components of the knee joint 10, and create a degree of slack in the affected medial and lateral tendons such that they are no longer able to maintain the femur 16 and tibia 18 in their proper stable alignment relative to the midplane 34. As a result, the patella 20 is no longer able to track in the V-shaped grooves 26, 28 between the femoral and tibial condyles 12, 22 during flexion of the knee joint 10, thereby leading to collateral damage.
When the femur 16 and tibia 18 are not correctly aligned, or if the meniscus 24, 25 is damaged, the femoral condyles 12 do not fit properly into the cavities of the meniscus 24, 25. In turn, this can cause the patella 20 to continually track improperly directly over the meniscus 24, 25 instead of through the V-shaped groove 28 of the tibial plateau. A relatively minor lateral shift of the patella 20 can decrease the surface contact area by 60%, and consequently increase the shear forces by 2½ times, depending on the sharpness or degree of the protrusion 30 on the underside of the patella 20 and the angle at which the protrusion 30 comes down on the meniscus 24, 25.
If the misalignment of the patella 20 is bad enough, the meniscus 24, 25 can be cut by the protrusion 30 to create a flap, wherein the flap can interfere with the flexion of the knee joint 10, and in some cases, get pinched during flexion, thereby causing extreme pain. Eventually, continued wear can result in shredding of the meniscus 24, 25, which can result in the meniscus 24, 25 being unable to contain the femoral condyles 12. Accordingly, once off track, the patella 20 can further irritate or injure the cartilage covering the condyles 12, 22, in addition to tearing or shredding the meniscus 24, 25. Any irritation or injury will initiate a typical body response of inflammation, pain and swelling. If this condition persists, the body may then mount an anti-inflammatory response to destroy or cordon off the inflamed tissue, thereby forming chondromalacia under the knee cap 20, more swelling and more fluid. This begins a vicious cycle in which the knee cartilage can be destroyed, and if left unchecked, the bones can be damaged.
Surgical intervention may be necessary to remove the flap of meniscus 24, 25 or to smooth out the shredded meniscus surface and to scrape off chondromalacia from the underside of the patella 20. Accordingly, the procedure generally reduces the size of the meniscus wall, thereby reducing the ability of the menisci 24, 25 to contain the femoral condyles 12 throughout a full range of motion of the knee joint 10. In addition, scraping the underside of the patella 20 can result in further irritation, and thus, can eventually result in more chondromalacia being formed. As a result, eventually, the knee joint 10 may need to be replaced.
The above-described condition of patello-femoral syndrome is commonly diagnosed by elimination. This is because the condition requires only a very small degree of misalignment of the femoral and tibial condyles 12, 22, the menisci 24, 25 and the tendons of the adjacent muscles. These changes are not normally detectable by MRI, CT scan, X-Ray or other non-invasive means. Yet, even a small correction of the misalignment back toward the proper alignment of the Q-angle, defined as the angle between the patellar tendon and the quadriceps, has an unexpectedly great decrease on the effects of the patello-femoral condition, and thus, a great decrease in the pain caused by misalignment.
Patello-femoral syndrome can be identified by knee arthroscopy, which is an invasive procedure. Arthroscopy can show chondromalacia of the patella 20, fluid in the knee capsule, cyst in the knee joint 10, and if great enough, both fluid and cysts may also be shown by MRI. Further, shredding and/or tearing of the menisci 24, 25 covering the tibial condyles 22 cannot be seen.
In an attempt to correct the small degree of misalignment in a knee joint 10, traditional knee braces are often used under a misconception that they are effective in correcting a patello-femoral condition. However, traditional knee braces are generally not effective in correcting the misalignment condition, or in lessening the pain associated therewith, since they typically apply equal and circumferentially uniform pressure on and around the knee joint 10 and the adjacent portions of both the lower and upper leg portions 14, 15. Some traditional braces have hinges to limit flexion of the knee joint 10 in bending and raising the lower leg portion 14, and also help to prevent side-to-side motion of the knee joint 10. Other knee braces have rigid side bars to further limit the range of motion of the knee joint 10 from side-to-side. Although these knee braces can be effective in restricting movement of the knee joint 10, they are largely ineffective in correcting a patello-femoral condition due to their application of equal and circumferentially uniform forces about the knee joint 10, and to their inability to realign misaligned femoral and tibial condyles.
Most of the less expensive knee braces are sleeve-type, which are generally both difficult to put on and uncomfortable after continued use. In addition, sleeve-type braces made of neoprene inhibit heat dissipation and restrict the flow of blood to and from the knee joint 10, and thus, often result in swelling and pain. Some of the sleeve-type braces include hinges to support the knee joint 10 along the medial and lateral sides, but they limit the natural side-to-side rotation of the femur 16 during flexion. This limited side-to-side movement can prevent the knee joint 10 from making a complete recovery from damage, thereby preventing it from returning to its normal range of motion. This can result in further complications by allowing the muscles to be trained to move the knee joint 10 in an unnatural motion. In addition, rigid side bar braces also prevent normal rotation of the femur 16 present in its normal 3-D path of movement, and thus, do not allow natural tracking of the knee joint 10. Accordingly, they can also be ineffective in correcting a patello-femoral syndrome condition.
To overcome the difficulties of putting on sleeve-type braces, wrap-around knee braces are commonly used. The wrap around knee braces presently available also apply equal and circumferentially uniform pressures on and around the knee joint 10, and thus, are equally ineffective in treating a patello-femoral syndrome condition. In known wrap-type knee braces, straps above and below the knee joint 10 extend from the same side of the knee brace and are wrapped around the leg in the same circumferential direction. This contributes to the effect of placing equally directed pull forces above and below the knee joint 10. Wrap-around knee braces that have a main body portion of the brace behind or posterior to the knee joint 10 primarily support the upper and lower portion of the tendons attached to the patella 20. As such, these function to stabilize the pulley action of the patella 20, and may allow some rotation of the femur 16, but also result in an unnatural motion of the patella 20 by restricting its range of movement. In addition, they do not affect the realignment of the femoral or the tibial condyles 12, 22. As mentioned, if the femoral and the tibial condyles 12, 22 are misaligned, even slightly, the patella 20 cannot track correctly, and it will eventually damage the cartilage, menisci and synovial tissue that covers the adjacent surfaces of the bones which move over each other during flexion of the knee joint 10.
Another known wrap around knee brace construction is shown in U.S. Pat. No. 5,873,848, in which three separate straps are used to impart a side force directly on the patella to realign the knee joint. One strap is first fastened above the knee joint, then another is fastened below the knee joint, while a third strap is fastened to the first and second straps, with the third strap engaging the patella to cause its realignment. Not only is this a complicated mechanism to apply, but it also attempts to correct a patello-femoral syndrome condition by applying a side force directly on the patella. Though this may provide temporary relief to symptoms associated with the patello-femoral syndrome condition, it is not believed to be the best way to correct the source of the problem associated with the condition, which is misalignment of the femoral condyles relative to the meniscus and tibial condyles, and not misalignment of the patella.
A knee brace constructed in accordance with the present invention overcomes or greatly minimizes any limitations of the knee braces described above, thereby allowing a knee-joint experiencing a patello-femoral syndrome condition to be properly realigned via a knee brace that is easily applied, wherein the knee brace does not directly act on the patella. As such, a knee brace in accordance with the invention prevents or reduces collateral damage to the knee joint, and possibly negates the necessity for invasive surgical procedures to correct the damaged knee joint, while also providing a most effective recovery of the damaged knee joint.